Several series of experiments are planned continuing work on the two neural peptides, Substance P and neurotensin, first isolated in this laboratory. Studies will be continued on the regulation of the release of immunoreactive Substance P and somatostatin in cultures of primary sensory neurons grown from cells dissociated from embryonic chick dorsal root ganglia. This culture system in which the concentration of immunoreactive Substance P increases more than 40-fold during the first two weeks after plating will also be utilized in an attempt to measure the incorporation of (35S) methinine into immunoreactive Substance P, and if possible, to study some aspects of the regulation of this incorporation. This newly developed culture system permitting the long-term survival of dissociated hypothalamic cells from fetal rats will be utilized to study the regulation of the conversion of (3H) androgen precursors to (3H) estrone. Studies will continue on the characterization of immunoreactive neurotensin and Substance P in plasma and various manipulations will be performed in an effort to alter these levels in a meaningful physiological manner. A more complete chemical characterization of immunoreactive neurotensin in calf pituitary tissue is also planned.